The present invention relates to a mobile data medium and a data exchange device to be used therewith.
Data media for a cash-free money transfer are known in a broad variety. They are mostly applied as cards including a memory to be loaded with certain data. Basically, data media of this type include a code authorizing the card owner to draw or write off money from an account. This for example applies to credit cards or cheque cards. For other applications, the memory of the data medium includes a predetermined number of value units each one releasing a certain product or service when the data medium communicates with a data exchange device. When a value unit is present, a release signal will be generated so that the product or the service may be called in. At the same time one or more value units are cleared. If the memory is empty, the data medium is void and will be discarded like a telephone card. Alternatively, the data card may be reloaded by means of a data exchange device. For example, this may be performed by means of a recharging machine which is suited to reload the data medium after having paid a certain amount of money bit inserting coins or bills. As far as data media are concerned authorizing the owner to conducting so-called subsidy sales or free services, the reloading of the memory may take place without paying money or writing off the balance of the owner's account.
The memory space of data media is obviously limited. The larger the number of data being available at the same time, the higher is the memory capacity or, respectively, the faster the memory empties. The number of reloading processes is limited alike.